Alona ossiani herricki Sinev, 2013

Lee, Sue Yeon, Yoo, Jung Sun & Kim, Seung Tae, 2017, Recent progress in studies of the Cladocera (Crustacea: Branchiopoda) of South Korea with seven new records for the Korean Peninsula, Journal of Species Research 6, pp. 227-246 : 240-242

7. Alona ossiani herricki Sinev, 2013 ( Fig. 9)

Material deposited to NIBR. 5 parthenogenetic females from Billbae pond (N 33.40374°, E 126.351°), Jeju-do, coll. in 28 Nov 2012 by A.A. Kotov and H.G. Jeong , NI BRIV0000812488 .

Other localities. A rock-pool with brackish water, mouth of Geum River (N 35.9942°, E 126.7349°), Jeollabuk-do, coll. in 23 May 2016 by unknown collector .

Parthenogenetic female. Body ( Fig. 9A) oval, of moderate height, maximum height at middle of body. Dorsal margin of carapace convex; postero-dorsal and postero-ventral angles broadly rounded. Posterior margin weakly convex. Postero-dorsal angle ( Fig. 9B) with 5-6 groups of large setules, with 4-7 setules in each, size of setules in each group increasing posteriorly. Head small, rostrum in lateral view narrow, protruding downwards. Ocellus of moderate size, compound eye larger than ocellus. Posterior margin of head shield as prominent, acute distal angle. Two major head pores ( Fig. 9C) of same size, with a narrow connection between them, postpore distance about two inter-pore distances in adults, lateral head pores minute. A small pore-like thickening located behind the posterior angle of head shield. Labral keel moderately wide, with a blunt apex and convex or polygonal anterior margin. Postabdomen ( Fig. 9D) large, moderately high, weakly narrowing distally, its length about 2.5 height. Ventral margin straight. Distal margin almost straight, distal angle rounded. Dorsal margin almost straight in postanal portion and weakly concave in anal one, with distal part about 2.5 times longer than preanal one, postanal portion 2.5 times longer than anal one. Preanal angle weakly expressed, postanal angle not defined. Postanal margin ( Fig. 9E) with 12-14 well-developed, singular sharp denticles, each with 1-7 (usually 3-5) spinules along anterior margin; size of denticles increasing distally. Length of longest denticles about 1.5 width of base of postabdominal claw. Postanal portion with 9-12 broad lateral fascicles of setules, posteriormost setule of each fascicle longest, thicker than others, slightly shorter than neighboring marginal denticles. Postabdominal claw ( Fig. 9F) of moderate length, slightly longer than preanal portion of postabdomen. Basal spine long and slender, about 0.25-0.3 length of the claw. Antenna I ( Fig. 9G) of moderate size, length about 2.5 width; cluster of 2-3 long setules at anterior face about one third of antenna I length, antennular sensory seta thin, more than 2/3 length of antenna I, arising terminally. Nine terminal aesthetascs, two longest little longer than antenna I itself. Antenna II ( Fig. 9H) with antennal formula: setae 0-0-3/1-1-3; spines proximal basal segment. Seta arising from proximal segment of endopod thin, reaching end of endopod. Seta arising from middle segment of endopod, of similar size to apical setae. A single apical seta on exopodit and on endopod with a very long spinule at articulation point. Spine on proximal segment of exopod almost as long as middle segment. Spines on apical segments shorter than apical segments. Limb I ( Fig. 9I) with IDL seta 1 large and broad, claw-like, strongly curved, slightly shorter than seta 2; IDL setae 2 and 3 with thin setules in distal part, seta 2 about 3/4 the length of seta 3. Endite 2 with a very long seta e, two times longer than seta f, almost as long as limb corm itself.

Ephippial female. Body slightly higher than in parthenogenetic female, with arched dorsal margin; ephippium yellow-brown, without a specific sculpture ( Fig. 9J).

Male. Body ( Fig. 9K) low oval, with maximum height at its middle. Postabdomen ( Fig. 9L) of moderate size, with almost parallel margins. Length about 2.5 height. Ventral margin straight. Postabdominal claw situated on a small protrusion in ventral portion of convex distal margin. The gonopores open above the protrusion; posteroventral and posterodorsal angles rounded. Dorsal margin weakly convex in postanal portion and weakly concave in anal one. Preanal angle weakly defined; postanal angle not defined. Distal portion of postabdomen two times longer than preanal one, postanal portion 2.5 times longer than anal one. Clusters of thin setules in place of female marginal denticles on postanal margin, single distinctive spine-like denticle at postanal angle ( Fig. 9M). Lateral fascicles of setules as in female. Postabdominal claw ( Fig. 9N) weakly curved, shorter than in female, as long as preanal margin. Basal spine about 0.25 length of claw. Antenna I ( Fig. 9O) more broad than in female, with 12 terminal aesthetascs. Male seta sub-terminal, about 1/3 length of antenna I. Limb I ( Fig. 9P) with U-shaped copulatory hook ( Fig. 9Q), half as long as limb itself. IDL ( Fig. 9R) with four setae: IDL seta 1 not hook-like, but still well-developed, about 1/2 length of IDL seta 2; IDL setae 2 and 3 much thinner and two times shorter than in female; male seta curved, as long as seta 2. Ventral face of limb under copulatory brush ( Fig. 9S) with row of about 20 stiff setules of moderate length, and outer face of endite 3 with a cluster of 3-4 shorter setules. Inner seta (1) of endite 3 thinner than in female, with long setules distally.

Notes. The affinis -group of Alona sensu lato includes two widely distributed species, Old World A. affinis and American A. ossiani Sinev 1998 , and several local endemics (see Sinev, 2013). Adequate differentiation of A. affinis and A. ossiani is based on the male morphology only. Studied males have a morphology typical for A. ossiani , i.e. presence of denticles at the anal margin of the postabdomen is characteristic of a common North American subspecies A. ossiani herricki Sinev, 2013 . Studied specimens have some minor differences from North American populations: (1) a higher IP/PP ratio in females, (2) longer and thinner setules on postero-ventral angle of valves, (3) postabdomen slightly narrowing distally and (4) IDL seta 1 being significantly shorter than seta 2, but inter-population variability in this taxon was never studied. To date A. ossiani herricki was known from the Americas only.

This is a new record for Korea. Its presence in South Korea could be explained either by (1) a trans-Beringian distribution range of A. ossiani herricki , or (2) a humaninduced introduction (as a possible scenario, by US military forces during the Korean War).